There are many types of fluid dispensing devices currently available. For example, one type of fluid dispensing device that is currently in widespread use is known as a positive displacement filler. Some positive displacement fillers employ a piston and cylinder arrangement to alternately draw and expel a fluid to be dispensed. The piston draws the fluid into the cylinder when it moves in one direction (e.g., a downward stroke), and expels the fluid from the cylinder when it moves in an opposite direction (e.g., an upward stroke). The expelled fluid enters the bottle or container through a tube connected to the cylinder. Other types of positive displacement fillers may employ rotary pumps or diaphragm pumps to alternately draw and expel the fluid.
Another type of fluid dispensing device is known as a time/pressure filler. Generally, the time/pressure filler includes a fluid reservoir which is maintained under a relatively constant pressure. The fluid is dispensed from the reservoir through a compressible tube. Fluid flow is shut off by a pinch type valve which squeezes and collapses the discharge line. A pre-determined volume of fluid is dispensed by opening the discharge line for a pre-determined period of time and then closing the line. If the pressure within the fluid reservoir is maintained at a constant level, an equal amount of fluid should be dispensed each time the cycle is repeated.
A third type of fluid dispensing device is known as a volumetric fluid dispensing device. These types of devices first measure a predetermined volume of fluid before dispensing the fluid into a bottle or container. Generally, a fill tube is disposed between the reservoir and the bottle that receives the predetermined volume of fluid to be dispensed. The fill tube may comprise a compressible tube with a pinch-type valve. When the fill tube fills to a specified level, which may be determined by one or more optical sensors, for example, the pinch-type valve opens to permit the measured fluid to flow through the fill tube and into the bottle or container. Once the fluid is dispensed, the valve closes to stop the flow of fluid until the fill tube once again holds the predetermined volume of fluid.
Another type of volumetric fluid dispensing device uses the net weight of a container or bottle that receives the dispensed fluid. Particularly, the empty bottle or container rests on a balance. As the fluid enters the bottle or container, the balance detects the change in the bottle's weight. When the balance detects that the bottle and fluid have achieved a specified weight, a pinch-type valve closes to stop the flow of fluid into the bottle or container.
Some types of volumetric fluid dispensing devices do not employ pinch valves in the fluid path. With such devices, fluid is still measured and dispensed similar to a volumetric fluid dispensing device. However, rather than use a pinch valve to stop the flow of fluid, these types of devices raise and lower system components to control the fluid flow.
Each of these types of fluid dispensing devices has their advantages, such as speed and/or accuracy, but they also have various disadvantages.